Population Changes of the Torresian Imperial-Pigeon<i>Ducuta spilorrhoa</i>Over Twenty-one Years on North Brook Island, North Queensland

Thorsborne, A.; Thorsborne, MG; Winter, J.

doi:10.1071/mu9880001

Cited by 9 publications

(8 citation statements)

References 11 publications

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“…Since one of the pigeons flew 80 km in one day at the beginning of its migration, and was presumably about to embark on a sea crossing of several hundred kilometres, there is no physiological reason why pied imperial-pigeons should be restricted to interpatch flights below 14.2 km. Indeed, since they roost in large numbers on reef islands up to 35 km offshore (Thorsborne et al 1988;King 1990), daily flights well above the maximum I observed are quite possible. It is also likely that the transmitters impeded movement of some birds, especially those fitted with harnesses, and so the rates and distances moved must be considered as minimum estimates.…”

Section: Interpatch Movement Ratesmentioning

confidence: 93%

Movements of frugivorous birds among fragmented rainforests in the Northern Territory, Australia

Price¹

2006

Wildl. Res.

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Rainforests in the Northern Territory occur as small patches, and the frugivorous birds that depend on them are thought to move among the patches. I attached radio-transmitters to 41 birds of four species captured in several locations near Darwin. I recorded 55 interpatch flights, and estimated flight rates as between once per day and five days for figbirds and pied imperial-pigeons. The flight rates for rose-crowned fruit-doves and yellow orioles were much lower, but no reliable estimate could be made. The median flight distance was 2.5 km but one in five flights were more than 10 km. In addition, one pigeon flew 220 km in preparation for migration from Australia. Birds often undertook exploratory flights, returning to the original patch. Birds of one species captured together usually flew to different locations. When birds left a patch, it was usually to a distant patch, rather than a near neighbour. These movement patterns demonstrate that frugivorous birds use the rainforest network in a complex way. The birds depend on a network of rainforest patches and the pigeons and figbirds probably disperse large quantities of seeds among the patches. The conservation of rainforest ecosystems in northern Australia will depend on the protection of the current configuration of patches rather than a representative set of patches.

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Section: Interpatch Movement Ratesmentioning

confidence: 93%

Movements of frugivorous birds among fragmented rainforests in the Northern Territory, Australia

Price¹

2006

Wildl. Res.

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“…It therefore seems plausible that the increase in number of Pigeons at the Dinah Beach roost-site between November and December was due to the arrival or return of pairs with young. Thorsborne et al (1988) suggested that juvenile recruitment is a probable cause of annual population peaks in the north-eastern Queensland population. The species is multi-brooded, at least in north-eastern Queensland, with pairs rearing up to three chicks in one season (Crome 1975).…”

Section: Discussionmentioning

confidence: 99%

“…One of the few bird species that breed in Australia and annually migrate to New Guinea for the winter months, the Torresian Imperial-Pigeon Ducula spilorrhoa occurs in three disjunct populations across northern Australia: north-eastern Queensland, the Top End of the Northern Territory, and the Kimberley district of Western Australia (Higgins & Davies 1996). The largest population, with counts suggesting at least 800 000 birds (Thorsborne et al 1988;Brothers & Bone 2012), breeds in north-eastern Queensland, and is considered fully migratory. In contrast, the relatively small population of the Kimberley district is known to be resident (Storr 1980;Johnstone 1981;King 1990).…”

Section: Introductionmentioning

confidence: 99%

Partial loss of migratory behaviour by Torresian ImperialPigeons Ducula spilorrhoa in Darwin, Northern Territory

Noske

Lilleyman

2016

Australian Field Ornithology

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The Northern Territory population of the Torresian Imperial-Pigeon Ducula spilorrhoa was once considered to be completely migratory, departing for New Guinea in February and returning to breed in August. However, reporting rates from Darwin suggest that since at least the early 1990s a substantial proportion of birds 'over-winter' in the region. We monitored an evening roost-site each month from May 2011 to August 2014, counting birds in 5-minute intervals as they arrived. Mean numbers were highest during the late wet-early dry season transition months (March through May) and lowest during the late dry-early wet season transition period (September through November), although the maximum number (1325 birds) was counted in June 2011, following the wettest wet season on record. These observations confirm that many Torresian Imperial-Pigeons do not migrate to New Guinea after the breeding season, but it is not yet known if any individual birds are long-term residents. It is possible that residency in the early dry season has evolved because of year-round availability of food resources in the urban environment but we were unable to test this hypothesis.

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“…It is known that they occasionally fly considerable distances (up to 300 km) in other parts of Australia (Frith 1982;Draffan et al . Pigeons were found to be mobile in the Kimberley, Western Australia (Johnstone & Burbidge 1991), and in island colonies in Queensland (Atherton & Greeves 1984;Thorsborne et al . The results of the present analysis do not suggest that pied imperial-pigeons are highly mobile, but, in part, this reflects a weakness in the analysis.…”

Section: Discussionmentioning

confidence: 99%

Indirect evidence that frugivorous birds track fluctuating fruit resources among rainforest patches in the Northern Territory, Australia

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2008

Austral Ecology

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Rainforests are naturally fragmented in the Northern Territory of Australia. A census of fruit and frugivorous bird abundance was taken monthly in 10 rainforest patches for 1 year and quarterly for a second year to investigate spatial and temporal patterns among the patches. Fruit abundance showed a marked annual cycle, with a peak around December in the wet season. Four of six bird species showed a significant seasonal fluctuation in abundance, and for three of them, these patterns were different among rainforest types. Three species also showed a significant tendency to be most abundant in the rainforest type with the most fruit in any month. We interpret these results as evidence that birds track fruit resources among rainforest patches of different types. The abundance of two of the species (figbird and pied imperial-pigeon) was highly variable and did not reveal significantly different temporal trends among rainforest types. These species are probably even more mobile than the other species, although the data in the present study cannot be used to test this theory. The conservation of frugivorous birds and of the plants whose seeds they disperse will require the protection of networks of rainforest patches.

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Population Changes of the Torresian Imperial-PigeonDucuta spilorrhoaOver Twenty-one Years on North Brook Island, North Queensland

Cited by 9 publications

References 11 publications

Movements of frugivorous birds among fragmented rainforests in the Northern Territory, Australia

Movements of frugivorous birds among fragmented rainforests in the Northern Territory, Australia

Partial loss of migratory behaviour by Torresian ImperialPigeons Ducula spilorrhoa in Darwin, Northern Territory

Indirect evidence that frugivorous birds track fluctuating fruit resources among rainforest patches in the Northern Territory, Australia

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